computer frying memory

Hi!
I've got a problem with a new 512mb memory I've bought. I've had to replace it three times because every time I insert it into my computer it just breaks.

I have a Epox Via KT266 motherboard and two 256mb sticks at the moment. These are all working fine.

The retailer I'm buying from are listing the 256 sticks as "Original" and the 512 as "Standard" (I guess that's the same as generic), and they are all Cas 2.5 and 266 chipset.

Since I've had three 512:s and they all have shown errors in memtest I'm guessing it's my computer that's frying them because no one can be this unlucky and get three faulty ones in a row.

Has anyone got an idea as to what might be the problem here? I know it's not a bad memory slot on the motherboard, because I've had different sticks in different slots each time.